You should maybe charge more than you think. Even if you’re committing to a few extra videos/posts/photos per month, having paying members takes extra work that is hard to account for. You should be compensated for that.
It’s rare for a member to convert from a lower tier to a higher tier. In most cases, it’s not worth it to have a way for people to pay you $2, $10, $50, in hopes that they’ll upgrade. If they’re happy with the $2 they’ll stay there. If they’re unhappy, they’re more likely to churn than upgrade.